The present invention relates to a device for sensing or controlling a function of materials, including liquids, solids, and gases, and which has particular advantages in the sensing of a level or flow of solid materials. Prior to the present invention there has been no completely satisfactory means for sensing the level of solid materials such as grain, gravel, or crushed stone, in bins and the like, nor the rate of flow of such materials. The indicating and/or control circuits for stopping and starting flows of solid materials usually require quite heavy currents that in turn make snap actuation of their controlling switches highly desirable. Another problem that has existed in such circuits is that snap actuating switches of the silicon controlled rectifier type have heretofore required separate and distinct control circuits for the gate of the rectifier, which circuits interrupt its normal operation at least momentarily to reset the silicon controlled rectifier (SCR) before the SCR can undertake its next cycle.
An object of the present invention therefore is the provision of a new and improved mechanism for sensing the level or the flow of solids, which is simple in design, rugged in its construction, and efficient in its operation, and which can be used to either indicate the presence of the solid and/or control the flow of the solid.
Another object of the invention is the provision of a new and improved control circuit for an electronic gate, the voltage drop across which increases, doubles back and increases again in generally an S-shaped curve as the through put current increases, and wherein the signal which controls the electronic gate automatically resets the electronic gate without extraneous circuitry.
A still further object of the present invention is the provision of a new and improved method for controlling a silicon controlled rectifier and the like, whereby the control signal is amplified and connected in series with the silicon controlled rectifier's power terminals while the control gate is provided with a generally constant voltage designed to limit the voltage differential between the breakover point and the reset voltage of the rectifier to fall within the negative and positive voltage swing of the amplifier.
Further objects and advantages of the invention will become apparent to those skilled in the art to which the invention relates from the following description of the preferred embodiments described with reference to the accompanying drawings forming a part of this specification.